Preparation of base-exchanging synthetic resin



Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE PREPARATION OFBASE-EXCHANGING SYN- THETIC RESIN No Drawing. Application December 3,1936, Serial No. 113,987

2 Claims.

The present invention relates to an improved method of producing aspecial type of resinous condensation product which has marked andvaluable base exchanging properties.

; One of the objects of the invention is to prepare a synthetic resinfrom a tannin and an aldehyde under such conditions as to produce theresin in the form in which it is particularly useful as a baseexchanging material.

) It has been found that certain types of resins produced from tanninand from aldehyde, when prepared under carefully controlled conditionsas set forth hereinbelow, have very marked base exchange properties; inother words, they will readily remove cations. After the cation removingproperties of these resins have become exhausted, they may very readilybe regenerated and rendered fit for re-use by treatment with diluteacid, such for example as hydrochloric acid, with a concentration offrom 0.5 up to 5%,

preferably at the lower range.

The present invention is carried out as hereinbelow set forth, theexample given being purely exemplary and not limiting.

; The preparation of a suitable material for this purpose may beaccomplished as follows:

50 parts by weight of what is known as crystalline quebracho tannin,which is a high grade tannin containing from 65% to 75% of actual tanninand is an unsulphited material, are dissolved in 500 parts by weight ofwater by vigorously stirring the solution to effect a complete mixtureof the materials, the mixture being heated during the stirring to justshort of the boiling 5 point until complete solution of the tannin inthe water has been secured. Thereupon 20 parts by weight of a 40%solution of formaldehyde are added to the mixture, which is contained ina suitable container provided with a reflux condenser, and the boilingcontinued for one hour, returning to the solution any of the water thatmight have escaped, so as to keep the material at constant volume. Theresultant solution is then with great rapidity introduced into 30 partsi by weight of concentrated hydrochloric acid, care being taken toefi'ect such rapid stirring of the acid as to secure an almost immediatecommingling of the materials. It is particularly important that thisstirring be suinciently violent to i avoid the formation of localconcentrations of material.

Almost immediately after the materials have thus been mixed,condensation will occur, with formation of resin, which causes theentire mixture to set into a relatively still gel. This gel is thenallowed to cool, is mechanically broken up by any suitable means, and isthen thoroughly Washed with water for the purpose of removing excesssoluble material. The gel may then be dried. In order to speed up thedrying, it is 5 within contemplation of the inventor to treat the gelafter washing with alcohol, followed by ether, in order to remove thewater therefrom. In any event the gel is dried by means of dry air at atemperature not exceeding 115 C. 1

When thus operating, there are obtained about 49 parts by weight of avery dark colored resin which corresponds to a yield of about 98% on thebasis of the weight of the original tannin used for carrying out theprocess.

This resin may be used for purposes of efl'ecting base exchange by usingit in a particle size that will pass through a 28-mesh sieve but will beretained on a 42-mesh sieve. Smaller particles are undesirable, as theyrender the filtering operation too difiicult, and particles much largerthan this do not possess suflicient surface in proportion to the weightof the material to be commercially practicable, although of course theinvention is not limited to the particle size of the resin when so used.

I claim:

1. The process of producing a base exchanging resin which comprisesboiling a mixture consisting of a tannin and formaldehyde under a refluxcondenser at constant volume for a period not substantially less thanone hour and then rapidly introducing the resulting product intoconcentrated hydrochloric acid under such conditions as to assure veryrapid and complete admixture, thereby forming a stiff gel, allowing thelatter to cool, comminuting it, then washing excess reagents therefromwith water, and drying the gel.

2. The process of making a base exchanging resin which comprisesdissolving 50 parts by weight of quebracho tannin in 500 parts by weightof water, adding 20 parts by weight of a 40% solution of formaldehyde.boiling the resultant mixture under a reflux condenser at constantvolume for a period of not substantially less than one'hour, introducingthe resultant solution rapidly into 30 parts by weight of concentratedhydrochloric acid under conditions to insure rapid and completeadmixture of the ingredients, thereby forming a gel, cooling the gel.comminuting the gel, washing it with water to remove excess solublematerials, and then drying the gel.

WIILARD H. KIRKPATRICK.

